DEMETRIA, in Grecian Antiquity, a festival in honour of Demeter (Ceres). An annual festival of the same name was instituted by the Athenians in B.C. 307, in honour of Demetrius Poliorcetes; and to honour that prince the more, they also changed the name of the Dionysia to Demetria. Athenæus (xii.) appears to refer to the Dionysia under their new name.